1 /* $OpenBSD: serverloop.c,v 1.159 2009/05/28 16:50:16 andreas Exp $ */
2 /*
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * All rights reserved
6 * Server main loop for handling the interactive session.
7 *
8 * As far as I am concerned, the code I have written for this software
9 * can be used freely for any purpose. Any derived versions of this
10 * software must be clearly marked as such, and if the derived work is
11 * incompatible with the protocol description in the RFC file, it must be
12 * called by a name other than "ssh" or "Secure Shell".
13 *
14 * SSH2 support by Markus Friedl.
15 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions
19 * are met:
20 * 1. Redistributions of source code must retain the above copyright
21 * notice, this list of conditions and the following disclaimer.
22 * 2. Redistributions in binary form must reproduce the above copyright
23 * notice, this list of conditions and the following disclaimer in the
24 * documentation and/or other materials provided with the distribution.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
27 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
29 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
30 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
31 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 */
37
38 #include <sys/param.h>
39 #include <sys/wait.h>
40 #include <sys/socket.h>
41 #include <sys/time.h>
42 #include <sys/queue.h>
43
44 #include <netinet/in.h>
45
46 #include <errno.h>
47 #include <fcntl.h>
48 #include <pwd.h>
49 #include <signal.h>
50 #include <string.h>
51 #include <termios.h>
52 #include <unistd.h>
53 #include <stdarg.h>
54
55 #include "xmalloc.h"
56 #include "packet.h"
57 #include "buffer.h"
58 #include "log.h"
59 #include "servconf.h"
60 #include "canohost.h"
61 #include "sshpty.h"
62 #include "channels.h"
63 #include "compat.h"
64 #include "ssh1.h"
65 #include "ssh2.h"
66 #include "key.h"
67 #include "cipher.h"
68 #include "kex.h"
69 #include "hostfile.h"
70 #include "auth.h"
71 #include "session.h"
72 #include "dispatch.h"
73 #include "auth-options.h"
74 #include "serverloop.h"
75 #include "misc.h"
76 #include "roaming.h"
77
78 __RCSID("$MirOS: src/usr.bin/ssh/serverloop.c,v 1.9 2009/10/04 14:29:07 tg Exp $");
79
80 extern ServerOptions options;
81
82 /* XXX */
83 extern Kex *xxx_kex;
84 extern Authctxt *the_authctxt;
85 extern int use_privsep;
86
87 static Buffer stdin_buffer; /* Buffer for stdin data. */
88 static Buffer stdout_buffer; /* Buffer for stdout data. */
89 static Buffer stderr_buffer; /* Buffer for stderr data. */
90 static int fdin; /* Descriptor for stdin (for writing) */
91 static int fdout; /* Descriptor for stdout (for reading);
92 May be same number as fdin. */
93 static int fderr; /* Descriptor for stderr. May be -1. */
94 static long stdin_bytes = 0; /* Number of bytes written to stdin. */
95 static long stdout_bytes = 0; /* Number of stdout bytes sent to client. */
96 static long stderr_bytes = 0; /* Number of stderr bytes sent to client. */
97 static long fdout_bytes = 0; /* Number of stdout bytes read from program. */
98 static int stdin_eof = 0; /* EOF message received from client. */
99 static int fdout_eof = 0; /* EOF encountered reading from fdout. */
100 static int fderr_eof = 0; /* EOF encountered readung from fderr. */
101 static int fdin_is_tty = 0; /* fdin points to a tty. */
102 static int connection_in; /* Connection to client (input). */
103 static int connection_out; /* Connection to client (output). */
104 static int connection_closed = 0; /* Connection to client closed. */
105 static u_int buffer_high; /* "Soft" max buffer size. */
106 static int no_more_sessions = 0; /* Disallow further sessions. */
107
108 /*
109 * This SIGCHLD kludge is used to detect when the child exits. The server
110 * will exit after that, as soon as forwarded connections have terminated.
111 */
112
113 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */
114
115 /* Cleanup on signals (!use_privsep case only) */
116 static volatile sig_atomic_t received_sigterm = 0;
117
118 /* prototypes */
119 static void server_init_dispatch(void);
120
121 /*
122 * we write to this pipe if a SIGCHLD is caught in order to avoid
123 * the race between select() and child_terminated
124 */
125 static int notify_pipe[2];
126 static void
notify_setup(void)127 notify_setup(void)
128 {
129 if (pipe(notify_pipe) < 0) {
130 error("pipe(notify_pipe) failed %s", strerror(errno));
131 } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) ||
132 (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) {
133 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
134 close(notify_pipe[0]);
135 close(notify_pipe[1]);
136 } else {
137 set_nonblock(notify_pipe[0]);
138 set_nonblock(notify_pipe[1]);
139 return;
140 }
141 notify_pipe[0] = -1; /* read end */
142 notify_pipe[1] = -1; /* write end */
143 }
144 static void
notify_parent(void)145 notify_parent(void)
146 {
147 if (notify_pipe[1] != -1)
148 write(notify_pipe[1], "", 1);
149 }
150 static void
notify_prepare(fd_set * readset)151 notify_prepare(fd_set *readset)
152 {
153 if (notify_pipe[0] != -1)
154 FD_SET(notify_pipe[0], readset);
155 }
156 static void
notify_done(fd_set * readset)157 notify_done(fd_set *readset)
158 {
159 char c;
160
161 if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
162 while (read(notify_pipe[0], &c, 1) != -1)
163 debug2("notify_done: reading");
164 }
165
166 /*ARGSUSED*/
167 static void
sigchld_handler(int sig)168 sigchld_handler(int sig)
169 {
170 int save_errno = errno;
171 child_terminated = 1;
172 signal(SIGCHLD, sigchld_handler);
173 notify_parent();
174 errno = save_errno;
175 }
176
177 /*ARGSUSED*/
178 static void
sigterm_handler(int sig)179 sigterm_handler(int sig)
180 {
181 received_sigterm = sig;
182 }
183
184 /*
185 * Make packets from buffered stderr data, and buffer it for sending
186 * to the client.
187 */
188 static void
make_packets_from_stderr_data(void)189 make_packets_from_stderr_data(void)
190 {
191 u_int len;
192
193 /* Send buffered stderr data to the client. */
194 while (buffer_len(&stderr_buffer) > 0 &&
195 packet_not_very_much_data_to_write()) {
196 len = buffer_len(&stderr_buffer);
197 if (packet_is_interactive()) {
198 if (len > 512)
199 len = 512;
200 } else {
201 /* Keep the packets at reasonable size. */
202 if (len > packet_get_maxsize())
203 len = packet_get_maxsize();
204 }
205 packet_start(SSH_SMSG_STDERR_DATA);
206 packet_put_string(buffer_ptr(&stderr_buffer), len);
207 packet_send();
208 buffer_consume(&stderr_buffer, len);
209 stderr_bytes += len;
210 }
211 }
212
213 /*
214 * Make packets from buffered stdout data, and buffer it for sending to the
215 * client.
216 */
217 static void
make_packets_from_stdout_data(void)218 make_packets_from_stdout_data(void)
219 {
220 u_int len;
221
222 /* Send buffered stdout data to the client. */
223 while (buffer_len(&stdout_buffer) > 0 &&
224 packet_not_very_much_data_to_write()) {
225 len = buffer_len(&stdout_buffer);
226 if (packet_is_interactive()) {
227 if (len > 512)
228 len = 512;
229 } else {
230 /* Keep the packets at reasonable size. */
231 if (len > packet_get_maxsize())
232 len = packet_get_maxsize();
233 }
234 packet_start(SSH_SMSG_STDOUT_DATA);
235 packet_put_string(buffer_ptr(&stdout_buffer), len);
236 packet_send();
237 buffer_consume(&stdout_buffer, len);
238 stdout_bytes += len;
239 }
240 }
241
242 static void
client_alive_check(void)243 client_alive_check(void)
244 {
245 int channel_id;
246
247 /* timeout, check to see how many we have had */
248 if (packet_inc_alive_timeouts() > options.client_alive_count_max) {
249 logit("Timeout, client not responding.");
250 cleanup_exit(255);
251 }
252
253 /*
254 * send a bogus global/channel request with "wantreply",
255 * we should get back a failure
256 */
257 if ((channel_id = channel_find_open()) == -1) {
258 packet_start(SSH2_MSG_GLOBAL_REQUEST);
259 packet_put_cstring("keepalive@openssh.com");
260 packet_put_char(1); /* boolean: want reply */
261 } else {
262 channel_request_start(channel_id, "keepalive@openssh.com", 1);
263 }
264 packet_send();
265 }
266
267 /*
268 * Sleep in select() until we can do something. This will initialize the
269 * select masks. Upon return, the masks will indicate which descriptors
270 * have data or can accept data. Optionally, a maximum time can be specified
271 * for the duration of the wait (0 = infinite).
272 */
273 static void
wait_until_can_do_something(fd_set ** readsetp,fd_set ** writesetp,int * maxfdp,u_int * nallocp,u_int max_time_milliseconds)274 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
275 u_int *nallocp, u_int max_time_milliseconds)
276 {
277 struct timeval tv, *tvp;
278 int ret;
279 int client_alive_scheduled = 0;
280
281 /*
282 * if using client_alive, set the max timeout accordingly,
283 * and indicate that this particular timeout was for client
284 * alive by setting the client_alive_scheduled flag.
285 *
286 * this could be randomized somewhat to make traffic
287 * analysis more difficult, but we're not doing it yet.
288 */
289 if (compat20 &&
290 max_time_milliseconds == 0 && options.client_alive_interval) {
291 client_alive_scheduled = 1;
292 max_time_milliseconds = options.client_alive_interval * 1000;
293 }
294
295 /* Allocate and update select() masks for channel descriptors. */
296 channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0);
297
298 if (compat20) {
299 #if 0
300 /* wrong: bad condition XXX */
301 if (channel_not_very_much_buffered_data())
302 #endif
303 FD_SET(connection_in, *readsetp);
304 } else {
305 /*
306 * Read packets from the client unless we have too much
307 * buffered stdin or channel data.
308 */
309 if (buffer_len(&stdin_buffer) < buffer_high &&
310 channel_not_very_much_buffered_data())
311 FD_SET(connection_in, *readsetp);
312 /*
313 * If there is not too much data already buffered going to
314 * the client, try to get some more data from the program.
315 */
316 if (packet_not_very_much_data_to_write()) {
317 if (!fdout_eof)
318 FD_SET(fdout, *readsetp);
319 if (!fderr_eof)
320 FD_SET(fderr, *readsetp);
321 }
322 /*
323 * If we have buffered data, try to write some of that data
324 * to the program.
325 */
326 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
327 FD_SET(fdin, *writesetp);
328 }
329 notify_prepare(*readsetp);
330
331 /*
332 * If we have buffered packet data going to the client, mark that
333 * descriptor.
334 */
335 if (packet_have_data_to_write())
336 FD_SET(connection_out, *writesetp);
337
338 /*
339 * If child has terminated and there is enough buffer space to read
340 * from it, then read as much as is available and exit.
341 */
342 if (child_terminated && packet_not_very_much_data_to_write())
343 if (max_time_milliseconds == 0 || client_alive_scheduled)
344 max_time_milliseconds = 100;
345
346 if (max_time_milliseconds == 0)
347 tvp = NULL;
348 else {
349 tv.tv_sec = max_time_milliseconds / 1000;
350 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
351 tvp = &tv;
352 }
353
354 /* Wait for something to happen, or the timeout to expire. */
355 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
356
357 if (ret == -1) {
358 memset(*readsetp, 0, *nallocp);
359 memset(*writesetp, 0, *nallocp);
360 if (errno != EINTR)
361 error("select: %.100s", strerror(errno));
362 } else if (ret == 0 && client_alive_scheduled)
363 client_alive_check();
364
365 notify_done(*readsetp);
366 }
367
368 /*
369 * Processes input from the client and the program. Input data is stored
370 * in buffers and processed later.
371 */
372 static void
process_input(fd_set * readset)373 process_input(fd_set *readset)
374 {
375 int len;
376 char buf[16384];
377
378 /* Read and buffer any input data from the client. */
379 if (FD_ISSET(connection_in, readset)) {
380 int cont = 0;
381 len = roaming_read(connection_in, buf, sizeof(buf), &cont);
382 if (len == 0) {
383 if (cont)
384 return;
385 verbose("Connection closed by %.100s",
386 get_remote_ipaddr());
387 connection_closed = 1;
388 if (compat20)
389 return;
390 cleanup_exit(255);
391 } else if (len < 0) {
392 if (errno != EINTR && errno != EAGAIN) {
393 verbose("Read error from remote host "
394 "%.100s: %.100s",
395 get_remote_ipaddr(), strerror(errno));
396 cleanup_exit(255);
397 }
398 } else {
399 /* Buffer any received data. */
400 packet_process_incoming(buf, len);
401 }
402 }
403 if (compat20)
404 return;
405
406 /* Read and buffer any available stdout data from the program. */
407 if (!fdout_eof && FD_ISSET(fdout, readset)) {
408 len = read(fdout, buf, sizeof(buf));
409 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
410 /* do nothing */
411 } else if (len <= 0) {
412 fdout_eof = 1;
413 } else {
414 buffer_append(&stdout_buffer, buf, len);
415 fdout_bytes += len;
416 }
417 }
418 /* Read and buffer any available stderr data from the program. */
419 if (!fderr_eof && FD_ISSET(fderr, readset)) {
420 len = read(fderr, buf, sizeof(buf));
421 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
422 /* do nothing */
423 } else if (len <= 0) {
424 fderr_eof = 1;
425 } else {
426 buffer_append(&stderr_buffer, buf, len);
427 }
428 }
429 }
430
431 /*
432 * Sends data from internal buffers to client program stdin.
433 */
434 static void
process_output(fd_set * writeset)435 process_output(fd_set *writeset)
436 {
437 struct termios tio;
438 u_char *data;
439 u_int dlen;
440 int len;
441
442 /* Write buffered data to program stdin. */
443 if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
444 data = buffer_ptr(&stdin_buffer);
445 dlen = buffer_len(&stdin_buffer);
446 len = write(fdin, data, dlen);
447 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
448 /* do nothing */
449 } else if (len <= 0) {
450 if (fdin != fdout)
451 close(fdin);
452 else
453 shutdown(fdin, SHUT_WR); /* We will no longer send. */
454 fdin = -1;
455 } else {
456 /* Successful write. */
457 if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
458 tcgetattr(fdin, &tio) == 0 &&
459 !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
460 /*
461 * Simulate echo to reduce the impact of
462 * traffic analysis
463 */
464 packet_send_ignore(len);
465 packet_send();
466 }
467 /* Consume the data from the buffer. */
468 buffer_consume(&stdin_buffer, len);
469 /* Update the count of bytes written to the program. */
470 stdin_bytes += len;
471 }
472 }
473 /* Send any buffered packet data to the client. */
474 if (FD_ISSET(connection_out, writeset))
475 packet_write_poll();
476 }
477
478 /*
479 * Wait until all buffered output has been sent to the client.
480 * This is used when the program terminates.
481 */
482 static void
drain_output(void)483 drain_output(void)
484 {
485 /* Send any buffered stdout data to the client. */
486 if (buffer_len(&stdout_buffer) > 0) {
487 packet_start(SSH_SMSG_STDOUT_DATA);
488 packet_put_string(buffer_ptr(&stdout_buffer),
489 buffer_len(&stdout_buffer));
490 packet_send();
491 /* Update the count of sent bytes. */
492 stdout_bytes += buffer_len(&stdout_buffer);
493 }
494 /* Send any buffered stderr data to the client. */
495 if (buffer_len(&stderr_buffer) > 0) {
496 packet_start(SSH_SMSG_STDERR_DATA);
497 packet_put_string(buffer_ptr(&stderr_buffer),
498 buffer_len(&stderr_buffer));
499 packet_send();
500 /* Update the count of sent bytes. */
501 stderr_bytes += buffer_len(&stderr_buffer);
502 }
503 /* Wait until all buffered data has been written to the client. */
504 packet_write_wait();
505 }
506
507 static void
process_buffered_input_packets(void)508 process_buffered_input_packets(void)
509 {
510 dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
511 }
512
513 /*
514 * Performs the interactive session. This handles data transmission between
515 * the client and the program. Note that the notion of stdin, stdout, and
516 * stderr in this function is sort of reversed: this function writes to
517 * stdin (of the child program), and reads from stdout and stderr (of the
518 * child program).
519 */
520 void
server_loop(pid_t pid,int fdin_arg,int fdout_arg,int fderr_arg)521 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
522 {
523 fd_set *readset = NULL, *writeset = NULL;
524 int max_fd = 0;
525 u_int nalloc = 0;
526 int wait_status; /* Status returned by wait(). */
527 pid_t wait_pid; /* pid returned by wait(). */
528 int waiting_termination = 0; /* Have displayed waiting close message. */
529 u_int max_time_milliseconds;
530 u_int previous_stdout_buffer_bytes;
531 u_int stdout_buffer_bytes;
532 int type;
533
534 debug("Entering interactive session.");
535
536 /* Initialize the SIGCHLD kludge. */
537 child_terminated = 0;
538 signal(SIGCHLD, sigchld_handler);
539
540 if (!use_privsep) {
541 signal(SIGTERM, sigterm_handler);
542 signal(SIGINT, sigterm_handler);
543 signal(SIGQUIT, sigterm_handler);
544 }
545
546 /* Initialize our global variables. */
547 fdin = fdin_arg;
548 fdout = fdout_arg;
549 fderr = fderr_arg;
550
551 /* nonblocking IO */
552 set_nonblock(fdin);
553 set_nonblock(fdout);
554 /* we don't have stderr for interactive terminal sessions, see below */
555 if (fderr != -1)
556 set_nonblock(fderr);
557
558 if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
559 fdin_is_tty = 1;
560
561 connection_in = packet_get_connection_in();
562 connection_out = packet_get_connection_out();
563
564 notify_setup();
565
566 previous_stdout_buffer_bytes = 0;
567
568 /* Set approximate I/O buffer size. */
569 if (packet_is_interactive())
570 buffer_high = 4096;
571 else
572 buffer_high = 64 * 1024;
573
574 #if 0
575 /* Initialize max_fd to the maximum of the known file descriptors. */
576 max_fd = MAX(connection_in, connection_out);
577 max_fd = MAX(max_fd, fdin);
578 max_fd = MAX(max_fd, fdout);
579 if (fderr != -1)
580 max_fd = MAX(max_fd, fderr);
581 #endif
582
583 /* Initialize Initialize buffers. */
584 buffer_init(&stdin_buffer);
585 buffer_init(&stdout_buffer);
586 buffer_init(&stderr_buffer);
587
588 /*
589 * If we have no separate fderr (which is the case when we have a pty
590 * - there we cannot make difference between data sent to stdout and
591 * stderr), indicate that we have seen an EOF from stderr. This way
592 * we don't need to check the descriptor everywhere.
593 */
594 if (fderr == -1)
595 fderr_eof = 1;
596
597 server_init_dispatch();
598
599 /* Main loop of the server for the interactive session mode. */
600 for (;;) {
601
602 /* Process buffered packets from the client. */
603 process_buffered_input_packets();
604
605 /*
606 * If we have received eof, and there is no more pending
607 * input data, cause a real eof by closing fdin.
608 */
609 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
610 if (fdin != fdout)
611 close(fdin);
612 else
613 shutdown(fdin, SHUT_WR); /* We will no longer send. */
614 fdin = -1;
615 }
616 /* Make packets from buffered stderr data to send to the client. */
617 make_packets_from_stderr_data();
618
619 /*
620 * Make packets from buffered stdout data to send to the
621 * client. If there is very little to send, this arranges to
622 * not send them now, but to wait a short while to see if we
623 * are getting more data. This is necessary, as some systems
624 * wake up readers from a pty after each separate character.
625 */
626 max_time_milliseconds = 0;
627 stdout_buffer_bytes = buffer_len(&stdout_buffer);
628 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
629 stdout_buffer_bytes != previous_stdout_buffer_bytes) {
630 /* try again after a while */
631 max_time_milliseconds = 10;
632 } else {
633 /* Send it now. */
634 make_packets_from_stdout_data();
635 }
636 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
637
638 /* Send channel data to the client. */
639 if (packet_not_very_much_data_to_write())
640 channel_output_poll();
641
642 /*
643 * Bail out of the loop if the program has closed its output
644 * descriptors, and we have no more data to send to the
645 * client, and there is no pending buffered data.
646 */
647 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
648 buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
649 if (!channel_still_open())
650 break;
651 if (!waiting_termination) {
652 const char *s = "Waiting for forwarded connections to terminate...\r\n";
653 char *cp;
654 waiting_termination = 1;
655 buffer_append(&stderr_buffer, s, strlen(s));
656
657 /* Display list of open channels. */
658 cp = channel_open_message();
659 buffer_append(&stderr_buffer, cp, strlen(cp));
660 xfree(cp);
661 }
662 }
663 max_fd = MAX(connection_in, connection_out);
664 max_fd = MAX(max_fd, fdin);
665 max_fd = MAX(max_fd, fdout);
666 max_fd = MAX(max_fd, fderr);
667 max_fd = MAX(max_fd, notify_pipe[0]);
668
669 /* Sleep in select() until we can do something. */
670 wait_until_can_do_something(&readset, &writeset, &max_fd,
671 &nalloc, max_time_milliseconds);
672
673 if (received_sigterm) {
674 logit("Exiting on signal %d", received_sigterm);
675 /* Clean up sessions, utmp, etc. */
676 cleanup_exit(255);
677 }
678
679 /* Process any channel events. */
680 channel_after_select(readset, writeset);
681
682 /* Process input from the client and from program stdout/stderr. */
683 process_input(readset);
684
685 /* Process output to the client and to program stdin. */
686 process_output(writeset);
687 }
688 if (readset)
689 xfree(readset);
690 if (writeset)
691 xfree(writeset);
692
693 /* Cleanup and termination code. */
694
695 /* Wait until all output has been sent to the client. */
696 drain_output();
697
698 debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
699 stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
700
701 /* Free and clear the buffers. */
702 buffer_free(&stdin_buffer);
703 buffer_free(&stdout_buffer);
704 buffer_free(&stderr_buffer);
705
706 /* Close the file descriptors. */
707 if (fdout != -1)
708 close(fdout);
709 fdout = -1;
710 fdout_eof = 1;
711 if (fderr != -1)
712 close(fderr);
713 fderr = -1;
714 fderr_eof = 1;
715 if (fdin != -1)
716 close(fdin);
717 fdin = -1;
718
719 channel_free_all();
720
721 /* We no longer want our SIGCHLD handler to be called. */
722 signal(SIGCHLD, SIG_DFL);
723
724 while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
725 if (errno != EINTR)
726 packet_disconnect("wait: %.100s", strerror(errno));
727 if (wait_pid != pid)
728 error("Strange, wait returned pid %ld, expected %ld",
729 (long)wait_pid, (long)pid);
730
731 /* Check if it exited normally. */
732 if (WIFEXITED(wait_status)) {
733 /* Yes, normal exit. Get exit status and send it to the client. */
734 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
735 packet_start(SSH_SMSG_EXITSTATUS);
736 packet_put_int(WEXITSTATUS(wait_status));
737 packet_send();
738 packet_write_wait();
739
740 /*
741 * Wait for exit confirmation. Note that there might be
742 * other packets coming before it; however, the program has
743 * already died so we just ignore them. The client is
744 * supposed to respond with the confirmation when it receives
745 * the exit status.
746 */
747 do {
748 type = packet_read();
749 }
750 while (type != SSH_CMSG_EXIT_CONFIRMATION);
751
752 debug("Received exit confirmation.");
753 return;
754 }
755 /* Check if the program terminated due to a signal. */
756 if (WIFSIGNALED(wait_status))
757 packet_disconnect("Command terminated on signal %d.",
758 WTERMSIG(wait_status));
759
760 /* Some weird exit cause. Just exit. */
761 packet_disconnect("wait returned status %04x.", wait_status);
762 /* NOTREACHED */
763 }
764
765 static void
collect_children(void)766 collect_children(void)
767 {
768 pid_t pid;
769 sigset_t oset, nset;
770 int status;
771
772 /* block SIGCHLD while we check for dead children */
773 sigemptyset(&nset);
774 sigaddset(&nset, SIGCHLD);
775 sigprocmask(SIG_BLOCK, &nset, &oset);
776 if (child_terminated) {
777 debug("Received SIGCHLD.");
778 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
779 (pid < 0 && errno == EINTR))
780 if (pid > 0)
781 session_close_by_pid(pid, status);
782 child_terminated = 0;
783 }
784 sigprocmask(SIG_SETMASK, &oset, NULL);
785 }
786
787 void
server_loop2(Authctxt * authctxt)788 server_loop2(Authctxt *authctxt)
789 {
790 fd_set *readset = NULL, *writeset = NULL;
791 int rekeying = 0, max_fd, nalloc = 0;
792
793 debug("Entering interactive session for SSH2.");
794
795 signal(SIGCHLD, sigchld_handler);
796 child_terminated = 0;
797 connection_in = packet_get_connection_in();
798 connection_out = packet_get_connection_out();
799
800 if (!use_privsep) {
801 signal(SIGTERM, sigterm_handler);
802 signal(SIGINT, sigterm_handler);
803 signal(SIGQUIT, sigterm_handler);
804 }
805
806 notify_setup();
807
808 max_fd = MAX(connection_in, connection_out);
809 max_fd = MAX(max_fd, notify_pipe[0]);
810
811 server_init_dispatch();
812
813 for (;;) {
814 process_buffered_input_packets();
815
816 rekeying = (xxx_kex != NULL && !xxx_kex->done);
817
818 if (!rekeying && packet_not_very_much_data_to_write())
819 channel_output_poll();
820 wait_until_can_do_something(&readset, &writeset, &max_fd,
821 &nalloc, 0);
822
823 if (received_sigterm) {
824 logit("Exiting on signal %d", received_sigterm);
825 /* Clean up sessions, utmp, etc. */
826 cleanup_exit(255);
827 }
828
829 collect_children();
830 if (!rekeying) {
831 channel_after_select(readset, writeset);
832 if (packet_need_rekeying()) {
833 debug("need rekeying");
834 xxx_kex->done = 0;
835 kex_send_kexinit(xxx_kex);
836 }
837 }
838 process_input(readset);
839 if (connection_closed)
840 break;
841 process_output(writeset);
842 }
843 collect_children();
844
845 if (readset)
846 xfree(readset);
847 if (writeset)
848 xfree(writeset);
849
850 /* free all channels, no more reads and writes */
851 channel_free_all();
852
853 /* free remaining sessions, e.g. remove wtmp entries */
854 session_destroy_all(NULL);
855 }
856
857 static void
server_input_keep_alive(int type,u_int32_t seq,void * ctxt)858 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
859 {
860 debug("Got %d/%u for keepalive", type, seq);
861 /*
862 * reset timeout, since we got a sane answer from the client.
863 * even if this was generated by something other than
864 * the bogus CHANNEL_REQUEST we send for keepalives.
865 */
866 packet_set_alive_timeouts(0);
867 }
868
869 static void
server_input_stdin_data(int type,u_int32_t seq,void * ctxt)870 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
871 {
872 char *data;
873 u_int data_len;
874
875 /* Stdin data from the client. Append it to the buffer. */
876 /* Ignore any data if the client has closed stdin. */
877 if (fdin == -1)
878 return;
879 data = packet_get_string(&data_len);
880 packet_check_eom();
881 buffer_append(&stdin_buffer, data, data_len);
882 memset(data, 0, data_len);
883 xfree(data);
884 }
885
886 static void
server_input_eof(int type,u_int32_t seq,void * ctxt)887 server_input_eof(int type, u_int32_t seq, void *ctxt)
888 {
889 /*
890 * Eof from the client. The stdin descriptor to the
891 * program will be closed when all buffered data has
892 * drained.
893 */
894 debug("EOF received for stdin.");
895 packet_check_eom();
896 stdin_eof = 1;
897 }
898
899 static void
server_input_window_size(int type,u_int32_t seq,void * ctxt)900 server_input_window_size(int type, u_int32_t seq, void *ctxt)
901 {
902 u_int row = packet_get_int();
903 u_int col = packet_get_int();
904 u_int xpixel = packet_get_int();
905 u_int ypixel = packet_get_int();
906
907 debug("Window change received.");
908 packet_check_eom();
909 if (fdin != -1)
910 pty_change_window_size(fdin, row, col, xpixel, ypixel);
911 }
912
913 static Channel *
server_request_direct_tcpip(void)914 server_request_direct_tcpip(void)
915 {
916 Channel *c;
917 char *target, *originator;
918 u_short target_port, originator_port;
919
920 target = packet_get_string(NULL);
921 target_port = packet_get_int();
922 originator = packet_get_string(NULL);
923 originator_port = packet_get_int();
924 packet_check_eom();
925
926 debug("server_request_direct_tcpip: originator %s port %d, target %s "
927 "port %d", originator, originator_port, target, target_port);
928
929 /* XXX check permission */
930 c = channel_connect_to(target, target_port,
931 "direct-tcpip", "direct-tcpip");
932
933 xfree(originator);
934 xfree(target);
935
936 return c;
937 }
938
939 static Channel *
server_request_tun(void)940 server_request_tun(void)
941 {
942 Channel *c = NULL;
943 int mode, tun;
944 int sock;
945
946 mode = packet_get_int();
947 switch (mode) {
948 case SSH_TUNMODE_POINTOPOINT:
949 case SSH_TUNMODE_ETHERNET:
950 break;
951 default:
952 packet_send_debug("Unsupported tunnel device mode.");
953 return NULL;
954 }
955 if ((options.permit_tun & mode) == 0) {
956 packet_send_debug("Server has rejected tunnel device "
957 "forwarding");
958 return NULL;
959 }
960
961 tun = packet_get_int();
962 if (forced_tun_device != -1) {
963 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
964 goto done;
965 tun = forced_tun_device;
966 }
967 sock = tun_open(tun, mode);
968 if (sock < 0)
969 goto done;
970 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
971 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
972 c->datagram = 1;
973
974 done:
975 if (c == NULL)
976 packet_send_debug("Failed to open the tunnel device.");
977 return c;
978 }
979
980 static Channel *
server_request_session(void)981 server_request_session(void)
982 {
983 Channel *c;
984
985 debug("input_session_request");
986 packet_check_eom();
987
988 if (no_more_sessions) {
989 packet_disconnect("Possible attack: attempt to open a session "
990 "after additional sessions disabled");
991 }
992
993 /*
994 * A server session has no fd to read or write until a
995 * CHANNEL_REQUEST for a shell is made, so we set the type to
996 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all
997 * CHANNEL_REQUEST messages is registered.
998 */
999 c = channel_new("session", SSH_CHANNEL_LARVAL,
1000 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
1001 0, "server-session", 1);
1002 if (session_open(the_authctxt, c->self) != 1) {
1003 debug("session open failed, free channel %d", c->self);
1004 channel_free(c);
1005 return NULL;
1006 }
1007 channel_register_cleanup(c->self, session_close_by_channel, 0);
1008 return c;
1009 }
1010
1011 static void
server_input_channel_open(int type,u_int32_t seq,void * ctxt)1012 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
1013 {
1014 Channel *c = NULL;
1015 char *ctype;
1016 int rchan;
1017 u_int rmaxpack, rwindow, len;
1018
1019 ctype = packet_get_string(&len);
1020 rchan = packet_get_int();
1021 rwindow = packet_get_int();
1022 rmaxpack = packet_get_int();
1023
1024 debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1025 ctype, rchan, rwindow, rmaxpack);
1026
1027 if (strcmp(ctype, "session") == 0) {
1028 c = server_request_session();
1029 } else if (strcmp(ctype, "direct-tcpip") == 0) {
1030 c = server_request_direct_tcpip();
1031 } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1032 c = server_request_tun();
1033 }
1034 if (c != NULL) {
1035 debug("server_input_channel_open: confirm %s", ctype);
1036 c->remote_id = rchan;
1037 c->remote_window = rwindow;
1038 c->remote_maxpacket = rmaxpack;
1039 if (c->type != SSH_CHANNEL_CONNECTING) {
1040 packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1041 packet_put_int(c->remote_id);
1042 packet_put_int(c->self);
1043 packet_put_int(c->local_window);
1044 packet_put_int(c->local_maxpacket);
1045 packet_send();
1046 }
1047 } else {
1048 debug("server_input_channel_open: failure %s", ctype);
1049 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1050 packet_put_int(rchan);
1051 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1052 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1053 packet_put_cstring("open failed");
1054 packet_put_cstring("");
1055 }
1056 packet_send();
1057 }
1058 xfree(ctype);
1059 }
1060
1061 static void
server_input_global_request(int type,u_int32_t seq,void * ctxt)1062 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1063 {
1064 char *rtype;
1065 int want_reply;
1066 int success = 0, allocated_listen_port = 0;
1067
1068 rtype = packet_get_string(NULL);
1069 want_reply = packet_get_char();
1070 debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1071
1072 /* -R style forwarding */
1073 if (strcmp(rtype, "tcpip-forward") == 0) {
1074 struct passwd *pw;
1075 char *listen_address;
1076 u_short listen_port;
1077
1078 pw = the_authctxt->pw;
1079 if (pw == NULL || !the_authctxt->valid)
1080 fatal("server_input_global_request: no/invalid user");
1081 listen_address = packet_get_string(NULL);
1082 listen_port = (u_short)packet_get_int();
1083 debug("server_input_global_request: tcpip-forward listen %s port %d",
1084 listen_address, listen_port);
1085
1086 /* check permissions */
1087 if (!options.allow_tcp_forwarding ||
1088 no_port_forwarding_flag ||
1089 (!want_reply && listen_port == 0) ||
1090 (listen_port != 0 && listen_port < IPPORT_RESERVED &&
1091 pw->pw_uid != 0)) {
1092 success = 0;
1093 packet_send_debug("Server has disabled port forwarding.");
1094 } else {
1095 /* Start listening on the port */
1096 success = channel_setup_remote_fwd_listener(
1097 listen_address, listen_port,
1098 &allocated_listen_port, options.gateway_ports);
1099 }
1100 xfree(listen_address);
1101 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1102 char *cancel_address;
1103 u_short cancel_port;
1104
1105 cancel_address = packet_get_string(NULL);
1106 cancel_port = (u_short)packet_get_int();
1107 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1108 cancel_address, cancel_port);
1109
1110 success = channel_cancel_rport_listener(cancel_address,
1111 cancel_port);
1112 xfree(cancel_address);
1113 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
1114 no_more_sessions = 1;
1115 success = 1;
1116 }
1117 if (want_reply) {
1118 packet_start(success ?
1119 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1120 if (success && allocated_listen_port > 0)
1121 packet_put_int(allocated_listen_port);
1122 packet_send();
1123 packet_write_wait();
1124 }
1125 xfree(rtype);
1126 }
1127
1128 static void
server_input_channel_req(int type,u_int32_t seq,void * ctxt)1129 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1130 {
1131 Channel *c;
1132 int id, reply, success = 0;
1133 char *rtype;
1134
1135 id = packet_get_int();
1136 rtype = packet_get_string(NULL);
1137 reply = packet_get_char();
1138
1139 debug("server_input_channel_req: channel %d request %s reply %d",
1140 id, rtype, reply);
1141
1142 if ((c = channel_lookup(id)) == NULL)
1143 packet_disconnect("server_input_channel_req: "
1144 "unknown channel %d", id);
1145 if (!strcmp(rtype, "eow@openssh.com")) {
1146 packet_check_eom();
1147 chan_rcvd_eow(c);
1148 } else if ((c->type == SSH_CHANNEL_LARVAL ||
1149 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
1150 success = session_input_channel_req(c, rtype);
1151 if (reply) {
1152 packet_start(success ?
1153 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1154 packet_put_int(c->remote_id);
1155 packet_send();
1156 }
1157 xfree(rtype);
1158 }
1159
1160 static void
server_init_dispatch_20(void)1161 server_init_dispatch_20(void)
1162 {
1163 debug("server_init_dispatch_20");
1164 dispatch_init(&dispatch_protocol_error);
1165 dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1166 dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1167 dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1168 dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1169 dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1170 dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1171 dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1172 dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1173 dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1174 dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1175 /* client_alive */
1176 dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive);
1177 dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
1178 dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1179 dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1180 /* rekeying */
1181 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1182 }
1183 static void
server_init_dispatch_13(void)1184 server_init_dispatch_13(void)
1185 {
1186 debug("server_init_dispatch_13");
1187 dispatch_init(NULL);
1188 dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1189 dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1190 dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1191 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1192 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1193 dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1194 dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1195 dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1196 dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1197 }
1198 static void
server_init_dispatch_15(void)1199 server_init_dispatch_15(void)
1200 {
1201 server_init_dispatch_13();
1202 debug("server_init_dispatch_15");
1203 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1204 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1205 }
1206 static void
server_init_dispatch(void)1207 server_init_dispatch(void)
1208 {
1209 if (compat20)
1210 server_init_dispatch_20();
1211 else if (compat13)
1212 server_init_dispatch_13();
1213 else
1214 server_init_dispatch_15();
1215 }
1216